Self-assembled structure and membrane comprising block copolymer and process for producing the same by spin coating (IIIa)

ABSTRACT

Disclosed are self-assembled structures formed from self-assembling diblock copolymers of the formula (I): 
                         
wherein R 1 -R 4 , n, and m are as described herein, which find use in preparing nanoporous membranes. In embodiments of the self-assembled structure, the block copolymer self-assembles into a cylindrical morphology. Also disclosed is a method of preparing such self-assembled structure which involves spin coating a polymer solution containing the diblock copolymer to obtain a thin film, followed by solvent annealing of the film. Further disclosed is a method of preparing porous membranes from the self-assembled structures.

BACKGROUND OF THE INVENTION

Membranes, particularly nanoporous membranes, are known to haveapplications in a number of areas including filtration of biologicalfluids, removal of micropollutants, water softening, wastewatertreatment, retention of dyes, preparation of ultrapure water in theelectronics industry, and concentration of food, juice, or milk. Methodsinvolving block copolymers, which self-assemble into nanostructures,have been proposed for preparing nanoporous membranes. Whileself-assembled structures are advantageous in that they producemembranes with uniform pore size and pore size distribution, challengesor difficulties remain with the proposed block copolymers and methods.For example, in some of these methods, a film is produced first from ablock copolymer, which is then followed by the removal of one of theblocks of the block copolymer by employing a harsh chemical such as astrong acid or a strong base.

The foregoing indicates that there is an unmet need for membranes madefrom block copolymers that are capable of self-assembling intonanostructures and for a method for producing nanoporous membranes fromthese block copolymers, which does not require a removal of one of theblocks after a nanostructure is formed.

BRIEF SUMMARY OF THE INVENTION

The invention provides a self-assembled structure and a porous membranecomprising a diblock copolymer of the formula (I):

wherein:

R¹ is a poly(alkyleneoxide) group of the formula, —(CHR—CH₂—O)_(p)—R′,wherein p=2-6, R is H or methyl, and R′ is H, a C₁-C₆ alkyl group, or aC₃-C₁₁ cycloalkyl group;

R² is a C₆-C₂₀ aryl group or a heteroaryl group, optionally substitutedwith a substituent selected from hydroxy, amino, halo, alkoxy,alkylcarbonyl, alkoxycarbonyl, amido, and nitro;

one of R³ and R⁴ is a C₆-C₁₄ aryl group, optionally substituted with asubstituent selected from hydroxy, halo, amino, and nitro, and the otherof R³ and R⁴ is a C₁-C₂₂ alkoxy group, optionally substituted with asubstituent selected from carboxy, amino, mercapto, alkynyl, alkenyl,halo, azido, and heterocyclyl;

n and m are independently about 10 to about 2000.

The invention also provides a method for preparing the aboveself-assembled structure comprising:

(i) dissolving the diblock copolymer in a solvent system to obtain apolymer solution;

(ii) spin coating the polymer solution onto a substrate;

(iii) annealing the coating obtained in (ii) to obtain a self-assembledstructure; and optionally

(iv) washing the self-assembled structure obtained in (iii).

The invention also provides membranes prepared from the aboveself-assembled structure.

The present invention takes advantage of the ability of the blockcopolymers having thermodynamically incompatible blocks to undergo phaseseparation and self-assemble into nanostructures, thereby leading to theformation of nanoporous membranes having uniform porosity.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 depicts the overlaid traces of the Multi-angle Laser LightScattering (MALS) gel permeation chromatograms (GPC) of a homopolymer 1(a precursor to the diblock copolymer) and a diblock copolymer 2 inaccordance with an embodiment of the invention.

FIG. 2 depicts an AFM height image of a self-assembled structure formedfrom a diblock copolymer. The self-assembled structure was prepared byspin coating a solution of the diblock copolymer on a silicon wafer at2000 rpm. Hexagonal order of the self-assembled structure is evident atleast from the circled regions.

FIG. 3 depicts the AFM phase image of the self-assembled structuredepicted in FIG. 2. Hexagonal order of the self-assembled structure isevident at least from the circled regions.

FIG. 4 depicts the profile showing the domain size and periodicity ofthe self-assembled structure in one of the circled regions of thestructure.

FIG. 5 depicts the profile showing the domain size and periodicity ofthe self-assembled structure in another circled region of the structure.

DETAILED DESCRIPTION OF THE INVENTION

In an embodiment, the invention provides a self-assembled structure anda porous membrane comprising a diblock copolymer of the formula (I):

wherein:

R¹ is a poly(alkyleneoxide) group of the formula, —(CHR—CH₂—O)_(p)—R′,wherein p=2-6, R is H or methyl, and R′ is H, a C₁-C₆ alkyl group, or aC₃-C₁₁ cycloalkyl group;

R² is a C₆-C₂₀ aryl group or a heteroaryl group, optionally substitutedwith a substituent selected from hydroxy, amino, halo, alkoxy,alkylcarbonyl, alkoxycarbonyl, amido, and nitro;

one of R³ and R⁴ is a C₆-C₁₄ aryl group, optionally substituted with asubstituent selected from hydroxy, halo, amino, and nitro, and the otherof R³ and R⁴ is a C₁-C₂₂ alkoxy group, optionally substituted with asubstituent selected from carboxy, amino, mercapto, alkynyl, alkenyl,halo, azido, and heterocyclyl;

n and m are independently about 10 to about 2000.

In an embodiment, the invention provides a method for preparing aself-assembled structure comprising a diblock copolymer of the formula(I):

wherein:

R¹ is a poly(alkyleneoxide) group of the formula, —(CHR—CH₂—O)_(p)—R′,wherein p=2-6, R is H or methyl, and R′ is H, a C₁-C₆ alkyl group, or aC₃-C₁₁ cycloalkyl group;

R² is a C₆-C₂₀ aryl group or a heteroaryl group, optionally substitutedwith a substituent selected from hydroxy, amino, halo, alkoxy,alkylcarbonyl, alkoxycarbonyl, amido, and nitro;

one of R³ and R⁴ is a C₆-C₁₄ aryl group, optionally substituted with asubstituent selected from hydroxy, halo, amino, and nitro, and the otherof R³ and R⁴ is a C₁-C₂₂ alkoxy group, optionally substituted with asubstituent selected from carboxy, amino, mercapto, alkynyl, alkenyl,halo, azido, and heterocyclyl;

n and m are independently about 10 to about 2000;

the method comprising:

(i) dissolving the diblock copolymer in a solvent system to obtain apolymer solution;

(ii) spin coating the polymer solution onto a substrate;

(iii) annealing the coating obtained in (ii) to obtain a self-assembledstructure; and optionally

(iv) washing the self-assembled structure obtained in (iii).

A porous membrane can be prepared from the self-assembled structure viaconfined swelling leading to the generation of pores. Confined swellingis effected by an annealing step, which could be carried out either byexposing the self-assembled structure to a solvent vapor or by soakingin a liquid solvent.

In accordance with an embodiment, the above diblock copolymer is of theformula (Ia), where the monomers are exo isomers:

In any of the embodiments above, R is H.

In any of the embodiments above, p is 3-6.

In any of the embodiments above, R′ is a C₁-C₆ alkyl group.

In any of the embodiments above, R² is a C₆-C₁₀ aryl group, optionallysubstituted with a substituent selected from hydroxy, amino, halo,alkoxy, alkylcarbonyl, alkoxycarbonyl, amido, and nitro.

In an embodiment, R² is a phenyl group, optionally substituted with asubstituent selected from hydroxy, amino, halo, alkoxy, alkylcarbonyl,alkoxycarbonyl, amido, and nitro;

In any of the embodiments above, R³ is a C₆-C₁₄ aryl group, optionallysubstituted with a substituent selected from hydroxy, halo, amino, andnitro and R⁴ is a C₁-C₂₂ alkoxy group, optionally substituted with asubstituent selected from carboxy, amino, mercapto, alkynyl, alkenyl,halo, azido, and heterocyclyl.

In an embodiment, R³ is phenyl, optionally substituted with asubstituent selected from hydroxy, halo, amino, and nitro and R⁴ is aC₁-C₆ alkoxy group, optionally substituted with a substituent selectedfrom carboxy, amino, mercapto, alkynyl, alkenyl, halo, azido, andheterocyclyl.

In an embodiment, R³ is provided by the ROMP catalyst employed for thepolymerization of the monomers.

In an embodiment, R⁴ is a group provided by the vinyl ether compoundemployed for terminating the polymerization.

In accordance with the invention, the term “aryl” refers to a mono, bi,or tricyclic carbocyclic ring system having one, two, or three aromaticrings, for example, phenyl, naphthyl, anthracenyl, or biphenyl. The term“aryl” refers to an unsubstituted or substituted aromatic carbocyclicmoiety, as commonly understood in the art, and includes monocyclic andpolycyclic aromatics such as, for example, phenyl, biphenyl, naphthyl,anthracenyl, pyrenyl, and the like. An aryl moiety generally containsfrom, for example, 6 to 30 carbon atoms, preferably from 6 to 18 carbonatoms, more preferably from 6 to 14 carbon atoms and most preferablyfrom 6 to 10 carbon atoms. It is understood that the term aryl includescarbocyclic moieties that are planar and comprise 4n+2π electrons,according to Hückel's Rule, wherein n=1, 2, or 3.

In accordance with the invention, the term “heteroaryl” refers to acyclic aromatic radical having from five to ten ring atoms of which atleast one atom is O, S, or N, and the remaining atoms are carbon.Examples of heteroaryl radicals include pyridyl, pyrazinyl, pyrimidinyl,pyrrolyl, pyrazolyl, imidazolyl, thiazolyl, oxazolyl, isooxazolyl,thiadiazolyl, oxadiazolyl, thiophenyl, furanyl, quinolinyl, andisoquinolinyl. The term “heteroaryl” as used herein, means a monocyclicheteroaryl or a bicyclic heteroaryl. The monocyclic heteroaryl is afive- or six-membered ring. The five-membered ring consists of twodouble bonds and one sulfur, nitrogen or oxygen atom. Alternatively, thefive-membered ring has two double bonds and one, two, three or fournitrogen atoms and optionally one additional heteroatom selected fromoxygen or sulfur, and the others carbon atoms. The six-membered ringconsists of three double bonds, one, two, three or four nitrogen atoms,and the others carbon atoms. The bicyclic heteroaryl consists of amonocyclic heteroaryl fused to a phenyl, or a monocyclic heteroarylfused to a monocyclic cycloalkyl, or a monocyclic heteroaryl fused to amonocyclic cycloalkenyl, or a monocyclic heteroaryl fused to amonocyclic heteroaryl. The monocyclic and the bicyclic heteroaryl areconnected to the parent molecular moiety through any substitutable atomcontained within the monocyclic or the bicyclic heteroaryl. Themonocyclic and bicyclic heteroaryl groups of the present invention canbe substituted or unsubstituted. In addition, the nitrogen heteroatommay or may not be quaternized, and may or may not be oxidized to theN-oxide. Also, the nitrogen containing rings may or may not beN-protected. Representative examples of monocyclic heteroaryl include,but are not limited to, furanyl, imidazolyl, isoxazolyl, isothiazolyl,oxadiazolyl, oxazolyl, pyridinyl, pyridine-N-oxide, pyridazinyl,pyrimindinyl, pyrazinyl, pyrazolyl, pyrrolyl, tetrazolyl, thiadiazolyl,thiazolyl, thienyl, triazolyl, and triazinyl. Representative examples ofbicyclic heteroaryl groups include, but not limited to, benzothienyl,benzoxazolyl, benzimidazolyl, benzoxadiazolyl,6,7-dihydro-1,3-benzothiazolyl, imidazo[1,2-a]pyridinyl, indazolyl,1H-indazol-3-yl, indolyl, isoindolyl, isoquinolinyl, naphthyridinyl,pyridoimidazolyl, quinolinyl, quinolin-8-yl, and5,6,7,8-tetrahydroquinolin-5-yl.

The “alkyl” group could be linear or branched. In accordance with anembodiment, the alkyl group is preferably a C₁-C₂₂ alkyl. Examples ofalkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl,sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl,hexadecyl, and the like. This definition also applies wherever “alkyl”occurs such as in hydroxyalkyl, monohalo alkyl, dihalo alkyl, andtrihalo alkyl. The C₁-C₂₂ alkyl group can also be further substitutedwith a cycloalkyl group, e.g., a C₃-C₁₁ cycloalkyl group.

In any of the above embodiments, the “cycloalkyl” group can bemonocyclic or bicyclic. Examples of monocyclic cycloalkyl groups includecyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, andcyclooctyl. Examples of bicyclic cycloalkyl groups include those withone common ring carbon atom such as spirooctane, spirononane,spirodecane, and spiroundecane, and those with two common ring carbonatoms such as bicyclooctane, bicyclononane, bicyclodecane, andbicycloundecane. Any of the cycloalkyl groups could be optionallysubstituted with one or more alkyl groups, e.g., C₁-C₆ alkyl groups.

In accordance with an embodiment, the “alkoxy” group is preferably aC₁-C₂₂ alkoxy. Examples of alkoxy group include methoxy, ethoxy,n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy, tert-butoxy,n-pentoxy, isopentoxy, n-hexoxy, hexadecyloxy, and the like.

The term “halo” refers to a halogen selected from the group consistingof fluorine, chlorine, bromine, and iodine, preferably chlorine orbromine.

The term “heterocycle” or “heterocyclic” as used herein, means amonocyclic heterocycle or a bicyclic heterocycle. The monocyclicheterocycle is a three-, four-, five-, six- or seven-membered ringcontaining at least one heteroatom independently selected from the groupconsisting of O, N, N(H) and S. The three- or four-membered ringcontains zero or one double bond and a heteroatom selected from thegroup consisting of O, N, N(H) and S. The five-membered ring containszero or one double bond, and one, two or three heteroatoms selected fromthe group consisting of O, N, N(H) and S. The six-membered ring containszero, one or two double bonds and one, two or three heteroatoms selectedfrom the group consisting of O, N, N(H) and S. The seven-membered ringcontains zero, one, two, or three double bonds and one, two or threeheteroatoms selected from the group consisting of O, N, N(H) and S. Themonocyclic heterocycle can be unsubstituted or substituted and isconnected to the parent molecular moiety through any substitutablecarbon atom or any substitutable nitrogen atom contained within themonocyclic heterocycle. Representative examples of monocyclicheterocycle include, but are not limited to, azetidinyl, azepanyl,aziridinyl, diazepanyl, [1,4]diazepan-1-yl, 1,3-dioxanyl,1,3-dioxolanyl, 1,3-dithiolanyl, 1,3-dithianyl, homomorpholinyl,homopiperazinyl, imidazolinyl, imidazolidinyl, isothiazolinyl,isothiazolidinyl, isoxazolinyl, isoxazolidinyl, morpholinyl,oxadiazolinyl, oxadiazolidinyl, oxazohnyl, oxazolidinyl, piperazinyl,piperidinyl, pyranyl, pyrazolinyl, pyrazolidinyl, pyrrolinyl,pyrrolidinyl, tetrahydrofuranyl, tetrahydropyranyl, tetrahydrothienyl,thiadiazolinyl, thiadiazolidinyl, thiazolinyl, thiazolidinyl,thiomorpholinyl, 1,1-dioxidothiomorpholinyl (thiomorpholine sulfone),thiopyranyl, and trithianyl. The bicyclic heterocycle is a monocyclicheterocycle fused to a phenyl group, or a monocyclic heterocycle fusedto a monocyclic cycloalkyl, or a monocyclic heterocycle fused to amonocyclic cycloalkenyl, a monocyclic heterocycle fused to a monocyclicheterocycle, or a monocyclic heterocycle fused to a monocyclicheteroaryl. The bicyclic heterocycle is connected to the parentmolecular moiety through any substitutable carbon atom or anysubstitutable nitrogen atom contained within the bicyclic heterocycleand can be unsubstituted or substituted. Representative examples ofbicyclic heterocycle include, but are not limited to, benzodioxinyl,benzopyranyl, thiochromanyl, 2,3-dihydroindolyl, indolizinyl,pyranopyridinyl, 1,2,3,4-tetrahydroisoquinolinyl,1,2,3,4-tetrahydroquinolinyl, thiopyranopyridinyl,2-oxo-1,3-benzoxazolyl, 3-oxo-benzoxazinyl, 3-azabicyclo[3.2.0]heptyl,3,6-diazabicyclo[3.2.0]heptyl, octahydrocyclopenta[c]pyrrolyl,hexahydro-1H-furo[3,4-c]pyrrolyl, octahydropyrrolo[3,4-c]pyrrolyl,2,3-dihydrobenzofuran-7-yl, 2,3-dihydrobenzofuran-3-yl, and3,4-dihydro-2H-chromen-4-yl. The monocyclic or bicyclic heterocycles asdefined herein may have two of the non-adjacent carbon atoms connectedby a heteroatom selected from N, N(H), O or S, or an alkylene bridge ofbetween one and three additional carbon atoms. Representative examplesof monocyclic or bicyclic heterocycles that contain such connectionbetween two non-adjacent carbon atoms include, but not limited to,2-azabicyclo[2.2.2]octyl, 2-oxa-5-azabicyclo[2.2.2]octyl,2,5-diazabicyclo[2.2.2]octyl, 2-azabicyclo[2.2.1]heptyl,2-oxa-5-azabicyclo[2.2.1]heptyl, 2,5-diazabicyclo[2.2.1]heptyl,2-azabicyclo[2.1.1]hexyl, 5-azabicyclo[2.1.1]hexyl,3-azabicyclo[3.1.1]heptyl, 6-oxa-3-azabicyclo[3.1.1]heptyl,8-azabicyclo[3.2.1]octyl, 3-oxa-8-azabicyclo[3.2.1]octyl,1,4-diazabicyclo[3.2.2]nonyl, 1,4-diazatricyclo[4.3.1.1 3,8]undecyl,3,10-diazabicyclo[4.3.1]decyl, or 8-oxa-3-azabicyclo[3.2.1]octyl,octahydro-1H-4,7-methanoisoindolyl, andoctahydro-1H-4,7-epoxyisoindolyl. The nitrogen heteroatom may or may notbe quaternized, and may or may not be oxidized to the N-oxide. Inaddition, the nitrogen containing heterocyclic rings may or may not beN-protected.

Examples of heterocyclyl groups include pyridyl, piperidinyl,piperazinyl, pyrazinyl, pyrolyl, pyranyl, tetrahydropyranyl,tetrahydrothiopyranyl, pyrrolidinyl, furanyl, tetrahydrofuranyl,thiophenyl, tetrahydrothiophenyl, purinyl, pyrimidinyl, thiazolyl,thiazolidinyl, thiazolinyl, oxazolyl, triazolyl, tetrazolyl, tetrazinyl,benzoxazolyl, morpholinyl, thiophorpholinyl, quinolinyl, andisoquinolinyl.

Five-membered unsaturated heterocyclics with and without benzo: furanyl,thiopheneyl, pyrrolyl, pyrazolyl, pyrazolinyl, imidazolyl, imidazolinyl,dithiazolyl, furazanyl, 1,2,3-triazolyl, tetrazolyl, 1,2,4-triazolyl,oxadiazolyl, thiadiazolyl, isoxazolyl, isoxazolinyl, oxazolyl,oxazolinyl, phospholyl, isothiazolyl, thiazolyl, thiazolinyl,isothiazolyl, isothiazolidinyl, benzofuranyl, benzothiophenyl, indolyl,benzimidazolyl, benzoxazolinyl, and benzothiazolinyl.

Whenever a range of the number of atoms in a structure is indicated(e.g., a C₁₋₂₂) a C₁₋₁₂, C₁₋₈, C₁₋₆, or C₁₋₄ alkyl, alkoxy, etc.), it isspecifically contemplated that any sub-range or individual number ofcarbon atoms falling within the indicated range also can be used. Thus,for instance, the recitation of a range of 1-22 carbon atoms (e.g.,C₁-C₂₂), 1-20 carbon atoms (e.g., C₁-C₂₀), 1-18 carbon atoms (e.g.,C₁-C₂₀), 1-16 carbon atoms (e.g., C₁-C₁₆), 1-14 carbon atoms (e.g.,C₁-C₁₄), 1-12 carbon atoms (e.g., C₁-C₁₂), 1-10 carbon atoms (e.g.,C₁-C₁₀), 1-8 carbon atoms (e.g., C₁-C₈) 1-6 carbon atoms (e.g., C₁-C₆),1-4 carbon atoms (e.g., C₁-C₄), 1-3 carbon atoms (e.g., C₁-C₃), or 2-8carbon atoms (e.g., C₂-C₈) as used with respect to any chemical group(e.g., alkyl, alkoxy, alkylamino, etc.) referenced herein encompassesand specifically describes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 21, or 22 carbon atoms, as appropriate, aswell as any sub-range thereof, e.g., 1-2 carbon atoms, 1-3 carbon atoms,1-4 carbon atoms, 1-5 carbon atoms, 1-6 carbon atoms, 1-7 carbon atoms,1-8 carbon atoms, 1-9 carbon atoms, 1-10 carbon atoms, 1-11 carbonatoms, 1-12 carbon atoms, 1-13 carbon atoms, 1-14 carbon atoms, 1-15carbon atoms, 1-16 carbon atoms, 1-17 carbon atoms, 1-18 carbon atoms,1-19 carbon atoms, 1-20 carbon atoms, 1-21 carbon atoms, and 1-22 carbonatoms, and anything in between such as 2-3 carbon atoms, 2-4 carbonatoms, 2-5 carbon atoms, 2-6 carbon atoms, 2-7 carbon atoms, 2-8 carbonatoms, 2-9 carbon atoms, 2-10 carbon atoms, 2-11 carbon atoms, 2-12carbon atoms, 2-12 carbon atoms, 2-13 carbon atoms, 2-14 carbon atoms,2-15 carbon atoms, 2-16 carbon atoms, 2-17 carbon atoms, 2-18 carbonatoms, 2-19 carbon atoms, 2-20 carbon atoms, 2-21 carbon atoms, and 2-22carbon atoms, 3-4 carbon atoms, 3-5 carbon atoms, 3-6 carbon atoms, 3-7carbon atoms, 3-8 carbon atoms, 3-9 carbon atoms, 3-10 carbon atoms,3-11 carbon atoms, 3-12 carbon atoms, 3-13 carbon atoms, 3-14 carbonatoms, 3-15 carbon atoms, 3-16 carbon atoms, 3-17 carbon atoms, 3-18carbon atoms, 3-19 carbon atoms, 3-20 carbon atoms, 3-21 carbon atoms,and 3-22 carbon atoms, and 4-5 carbon atoms, 4-6 carbon atoms, 4-7carbon atoms, 4-8 carbon atoms, 4-9 carbon atoms, 4-10 carbon atoms,4-11 carbon atoms, 4-12 carbon atoms, 4-13 carbon atoms, 4-14 carbonatoms, 4-15 carbon atoms, 4-16 carbon atoms, 4-17 carbon atoms, 4-18carbon atoms, 4-19 carbon atoms, 4-20 carbon atoms, 4-21 carbon atoms,4-22 carbon atoms, etc., as appropriate.

In the above embodiments, “n” and “m” represent the average degree ofpolymerization of the respective monomers.

In accordance with embodiments, n is about 10 to about 1000, about 10 toabout 500, about 10 to about 250, about 20 to about 1000, about 20 toabout 500, about 20 to about 250, about 30 to about 1000, about 30 toabout 500, about 30 to about 250, about 40 to about 1000, about 40 toabout 500, about 40 to about 250, about 50 to about 1000, about 50 toabout 500, about 50 to about 250, about 60 to about 1000, about 60 toabout 500, or about 60 to about 250.

In any of the above embodiments, in is about 50 to about 2000, about 50to about 1500, about 50 to about 1000, about 100 to about 2000, about100 to about 1500, about 100 to about 1000, about 150 to about 2000,about 150 to about 1500, about 150 to about 1000, about 200 to about2000, about 200 to about 1500, or about 200 to about 1000.

In any of the above embodiments, n is typically about 30 to about 350,preferably about 70 to about 200, more preferably about 100 to about150.

In any of the above embodiments of the diblock copolymer, m is typicallyabout 150 to about 1775, preferably about 350 about 1000, and morepreferably about 500 to about 750.

The diblock copolymer can have any suitable total molecular weight, forexample, a number average molecular weight (M) of from about 40 kDa toabout 500 kDa; in certain embodiments, the diblock copolymer has anM_(n) of from about 75 kDa to about 300 kDa; in certain otherembodiments, the diblock copolymer has an M_(n) of about 250 kDa. In anembodiment, the diblock copolymer has an M_(n) of 233 kDa.

The carbon-carbon double bonds in the diblock copolymer can have anysuitable orientation, cis, trans, and they can be distributed in arandom manner.

The diblock copolymer may self-assemble into any suitable morphology,for example, but not limited to, spherical or body centered cubicmorphology, cylindrical morphology, lamellar morphology, or doublegyroid morphology. The type of nanostructure into which the copolymersself-assemble would depend, among others, on the volume fraction of thetwo blocks in the block copolymer as well as the nature of the solventsystem.

For example, at a polymer volume fraction ratio range (f_(A):f_(B)) ofthe two monomers of 37-50:63-50, formation of a lamellar morphologyinvolving a stack of layers of equivalent domain size is favored, at avolume fraction ratio range of 15-70:85-30, formation of a cylindricalmorphology where the minor polymer component forms cylinders in a matrixof major polymer block component is favored, and at a volume fractionratio range of 7-15:83-85, formation of body centered cubic phase wherethe minor polymer component forms spheres in a matrix of the majorpolymer block component is favored. At a volume fraction ratio range of33-37:67-33, formation of a double gyroid morphology is favored.

Cylindrical morphology includes a phase domain morphology havingdiscrete tubular or cylindrical shapes. The tubular or cylindricalshapes may be hexagonally packed on a hexagonal lattice. In embodiments,the cylindrical domain size is from about 5 nm to about 100 nm.

Lamellar morphology includes a phase domain morphology having layers ofalternating compositions that are generally oriented parallel withrespect to one another. In embodiments, the lamellar domain size is fromabout 5 nm to about 100 nm.

The double gyroid morphology comprises two interpenetrating continuousnetwork. In embodiments, the double gyroid domain size is from about 5nm to about 100 nm.

Spherical morphology or bcc morphology refers to a phase domainmorphology having spherical domains of one block arranged on a bodycentered cubic lattice in a matrix of the second block. In embodiments,the spherical morphology domain size is from about 5 nm to about 100 nm.

In an embodiment, the polymerized second monomer (bearing R²) and thepolymerized first monomer (bearing R¹) are present in the diblockcopolymer in any suitable volume fraction. For example, the % volumefraction of the first monomer to that of the second monomer can be inthe range of about 15:about 85 to about 30:about 70, preferably in therange of about 19:about 81 to about 25:about 75, and more preferablyabout 20:about 80. In an embodiment, the volume fraction of the secondmonomer is about 78%, and the mass fraction is about 74%, of the totalpolymer.

In an embodiment, the volume fraction of the second monomer to that ofthe first monomer is about 3.5:1, which favors the formation ofcylindrical morphology. The mass fraction of the second monomer to thatof the first monomer is about 3.4:1.

In a specific embodiment, the self-assembled structure and the membranecomprise a diblock copolymer of formula (I) has the following structure,in particular, wherein n is 150 and m is 675:

In an embodiment, the self-assembled structure and the membrane comprisethe diblock copolymer of formula (I) has the following structure wherethe monomers are in the exo configuration, in particular, wherein n is150 and m is 675:

The diblock copolymers described above can be prepared by a methodcomprising:

(i) polymerizing one of the two monomers of the formulas:

with a ring opening metathesis polymerization (ROMP) catalyst to obtaina ring-opened polymer having a living chain end;

(ii) polymerizing the other of the two monomers on the living end of thering-opened polymer obtained in (i) to obtain a diblock copolymer havinga living end; and

(iii) terminating the living end of the diblock copolymer obtained in(ii) with an optionally substituted alkyl vinyl ether.

In the above method, the monomer that is first polymerized is of theformula:

After the polymerization of the above monomer, the second monomer thatis polymerized thereon is a monomer of the formula:

The first monomer and the second monomer can be an exo or endostereochemical configuration. In an embodiment, the first and secondmonomers are of the exo configuration, e.g., a monomer having the exoisomer at 98% or higher.

In the first and second monomers, R¹ and R² are the same as describedabove for the diblock copolymer of formula (I). The first and secondmonomers are (oxa)norbornene (di)carboxylic imide derived monomers. Themonomers can be prepared by any suitable method, for example, startingfrom maleimide and furan via a Diels-Alder reaction, illustrated below:

The first monomer can be synthesized via Mitsunobu Coupling reaction, asillustrated below:

Alternatively, the first monomer can be synthesized by the reaction ofN-triethyleneglycol monomethylether maleimide with furan via aDiels-Alder reaction.

The second monomer can be synthesized via a Diels-Alder reaction betweenN-phenyl maleimide and furan in acetonitrile, as illustrated below.

The polymerization of the monomers is carried out by ring-opening olefinmetathesis polymerization (ROMP), in which a cyclic olefin monomer ispolymerized or copolymerized by ring-opening of the cyclic olefinmonomer. Typically a transition metal catalyst containing a carbeneligand mediates the metathesis reaction.

Any suitable ROMP catalyst can be used, for example, Grubbs' first,second, and third generation catalysts, Umicore, Hoveyda-Grubbs,Schrock, and Schrock-Hoveyda catalysts can be employed. Examples of suchcatalysts include the following:

In an embodiment, Grubbs' third generation catalysts are particularlysuitable due to their advantages such as stability in air, tolerance tomultiple functional groups, and/or fast polymerization initiation andpropagation rates. In addition, with the Grubbs' third generationcatalysts, the end groups can be engineered to accommodate anycompatible groups, and the catalyst can be recycled readily. A preferredexample of such a catalyst is:

The above third generation Grubbs catalyst (G2) may be obtainedcommercially or prepared from a Grubbs second generation catalyst asfollows:

The first monomer and the second monomer are polymerized sequentially toobtain the diblock copolymer. Any of the two monomers can be polymerizedfirst. For example, the first monomer can be polymerized first, followedby the second monomer. Alternatively, the second monomer can bepolymerized first, followed by the first monomer.

Typically, the monomers have a chemical purity of at least 95%,preferably 99% or greater, and more preferably 99.9% or greater. It ispreferred that the monomers are free of impurities that will interferewith the polymerization, e.g., impurities that will affect the ROMPcatalyst. Examples of such impurities include amines, thiols, acids,phosphines, and N-substituted maleimides.

The polymerization of the monomers is conducted in a suitable solvent,for example, solvents generally used for conducting ROMPpolymerizations. Examples of suitable solvents include aromatichydrocarbons such as benzene, toluene, and xylene, aliphatichydrocarbons such as n-pentane, hexane, and heptane, alicylichydrocarbons such as cyclohexane, and halogenated hydrocarbons such asdichloromethane, dichloroethane, dichloroethylene, tetrachloroethane,chlorobenzene, dichlorobenzene, and trichlorobenzene, as well asmixtures thereof.

When polymerization is carried out in the organic solvent, the monomerconcentration can be in the range of 1 to 50 wt %, preferably 2 to 45 wt%, and more preferably 3 to 40 wt %.

The polymerization can be carried out at any suitable temperature, forexample, from −20 to +100° C., preferably 10 to 80° C.

The polymerization can be carried out for any time suitable to obtainthe appropriate chain length of each of the blocks, which can be fromabout 1 minute to 100 hours.

The amount of catalyst can be chosen in any suitable amount. Forexample, the molar ratio of the catalyst to the monomer can be about1:10 to about 1:1000, preferably about 1:50 to 1:500, and morepreferably about 1:100 to about 1:200. For example, the molar ratio ofthe catalyst to the monomer could be 1:n and 1:m, where n and in are theaverage degrees of polymerization.

After the polymerization of the two monomers, the chain end of thediblock copolymer is terminated by adding an optionally substitutedalkyl vinyl ether to the polymerization mixture.

The diblock copolymer can be isolated by any suitable technique, forexample, precipitation with a nonsolvent.

The homopolymer formed during the preparation of the diblock copolymerand the diblock copolymer of the invention can be characterized for itsmolecular weight and molecular weight distribution by any knowntechniques. For example, a MALS-GPC technique can be employed. Thetechnique uses a mobile phase to elute, via a high pressure pump, apolymer solution through a bank of columns packed with a stationaryphase. The stationary phase separates the polymer sample according tothe chain size followed by detecting the polymer by three differentdetectors. A series of detectors can be employed, e.g., an Ultravioletdetector (UV-detector), followed by a multi-angle laser light scatteringdetector (MALS-detector), which in turn, is followed by a refractiveindex detector (RI-detector) in a row. The UV-detector measures thepolymer light absorption at 254 nm wavelength; the MALS-detectormeasures the scattered light from polymer chains relative to mobilephase.

The diblock copolymers of the invention are highly monodisperse. Forexample, the copolymers have an Mw/Mn of 1.01 to 1.2, preferably 1.05 to1.10.

The present invention provides a self-assembled structure and a membranecomprise a porous membrane comprising a diblock copolymer describedabove.

In an embodiment, the self-assembled structure is prepared by spincoating a solution of the diblock copolymer. To prepare theself-assembled structure, the diblock copolymer is first dissolved in asuitable solvent or solvent system and cast as a thin film by spincoating.

The polymer solution can be prepared by any suitable method known tothose skilled in the art. The diblock copolymer is added to the solventsystem and stirred until a homogeneous solution is obtained. If desired,the solution can be stirred for an extended time to allow the diblockcopolymer to assume its thermodynamically favorable structure in thesolution. The diblock copolymer is dissolved in a good solvent or amixture containing good solvents.

Embodiments of a suitable solvent system include a solvent or a mixtureof solvents selected from halogenated hydrocarbons, ethers, amides, andsulfoxides. In an embodiment, the solvent system includes a volatilesolvent, for example, a solvent having a boiling point less than 100° C.

For example, the solvent system includes a solvent or a mixture ofsolvents selected from dichloromethane, 1-chloropentane,1,1-dichloroethane, N,N-dimethylfoimamide (DMF), N,N-dimethylacetamide(DMA), N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO),tetrahydrofuran (THF), 1,3-dioxane, and 1,4-dioxane.

Thus, for example, a mixture of DMF and THF, a mixture of DMA and THF, amixture of DMSO and THF, a mixture of DMSO and 1-chloropentane, amixture of NMP and 1-chloropentane, a mixture of DMF and1-chloropentane, a mixture of 1,3-dioxane and THF, a mixture of1,4-dioxane and THF, or a mixture of 1,3- or 1,4 dioxane, DMF, and THFcan be employed as the solvent system.

In a preferred embodiment, a mixture of DMF and THF, a mixture of DMAand THF, a mixture of DMA and 1-chloropentane, a mixture of DMSO andTHF, a mixture of 1,3-dioxane and THF, a mixture of 1,4-dioxane and THF,can be employed as the solvent system.

In a more preferred embodiment, dichloromethane or a mixture of DMF andTHF can be used as the solvent system.

In the above embodiments, where a mixture of solvents is used as thesolvent system, the mixture can include any suitable ratio of thesolvents, for example, in a binary solvent mixture, either of thesolvents can be present in a volume ratio of 80/20, 75/25, 70/30, 65/35,60/40, 55/45, or 50/50, or any ratio therebetween. In a ternary solventsystem, any of the three solvents can be present in any suitable ratio,for example, a volume ratio of 80/10/10, 75/15/10, 70/20/10, 65/25/10,60/30/10, 55/25/30, 40/40/20, or 30/30/40 or any ratio therebetween.

The polymer solution can contain any suitable amount of the diblockcopolymer. In accordance with an embodiment, the polymer solutioncontains about 0.1 to about 2%, preferably about 0.5 to about 1.5%, andmore preferably about 0.8 to about 1.2% by weight of the diblockcopolymer. In an example, the polymer solution contains about 1% byweight of the diblock copolymer. The polymer concentration can controlthe thickness of the film, and hence the membrane, obtained from spincoating.

Spin coating typically involves depositing a small volume of a polymersolution onto a generally flat substrate, preferably onto the center ofthe substrate. The polymer solution can be deposited by the use of asyringe or dropper, or continuously deposited from a tank.

When the polymer solution is deposited, the substrate may be stationaryor spinning at a low speed, e.g., up to about 500 rpm. Following thedeposition of the polymer solution, the substrate is accelerated to ahigh speed, for example, about 3000 rpm or more. In an embodiment, thesubstrate is accelerated to spin speeds of about 1500 rpm to about 6000rpm. The polymer solution flows radially on the substrate owing to theaction of the centrifugal force exerted by the spinning, and the excessof the polymer solution is ejected off the edge of substrate. Once thedesired spinning speed is reached, the spinning speed is maintained fora suitable period of time, for example, for a period of 1 min to 1 h,preferably 1.5 min. The film that is formed on the substrate continuesto thin slowly until it reaches an equilibrium thickness or until itturns solid-like due to a rise in the viscosity of the solution as thesolvent evaporates therefrom. The thickness of the film can becontrolled by varying the spinning speed for a given polymerconcentration.

The film can be cast to any suitable thickness, typically about 50 nm toabout 500 nm thick, preferably about 100 to about 300 nm, and morepreferably about 100 nm.

The atmosphere maintained above the spinning substrate can be anysuitable atmosphere, for example, ambient atmosphere, an atmosphere ofcontrolled humidity and/or temperature, an inert gas atmosphere, or thecoating carried out under vacuum. In an embodiment, a solvent vaporatmosphere can be maintained to anneal and induce self-assembly of theblock copolymer.

Any suitable substrate can be used to spin coat the polymer solution.The substrate can be porous or nonporous. Examples of suitablesubstrates include glass, silicon wafer, metal plate, polymer or plasticfilm, and a plastic film, e.g., polyvinyl alcohol, coated on a glasssubstrate or on a silicon wafer.

The substrate surface has an influence on the resulting morphologyorientation, and the orientation or morphology outcome is determinedbased on the thermodynamic interaction between the substrate and eachblock within the diblock copolymer. If the substrate surface hasfavorable interaction with one of the two blocks, the diblock copolymerwill self-assemble in such a way that it maximizes the interaction byspreading and exposing the block that it has favorable interaction with.For example, in the case of cylinder morphology the cylinder willinterface with the substrate surface in which the cylinder will beparallel to the surface if the substrate has higher affinity to oneblock than the other. If the substrate surface has neutral or littleaffinity toward either block, the cylinders will be aligned normal tothe substrate.

The spin coated film is annealed in order to further advance or completethe self-assembling process, or microphase separation, of the diblockcopolymer. Annealing is carried out in the presence of a suitablesolvent vapor. Any of the solvents identified above for the solventsystem can be employed as a solvent vapor to carry out the annealing.For example, dichloromethane can be employed as a vapor.

Annealing can be carried out for any suitable length of time, forexample, 0.1 hour to 1 month or more, 5 hours to 15 days or more, or 10hours to 10 days or more. Optionally, the film is washed to remove anyresidual solvents to recover the self-assembled structure.

In an embodiment, the substrate, e.g., a polymeric substrate, can bedissolved away in a suitable solvent, thereby recovering the thin film.For example, where a thin film is cast on a silicon wafer with a SiO₂layer grown on top, the SiO₂ layer can be dissolved in hydrofluoric acidto release and recover the thin film of the block copolymer.

In an embodiment, the recovered film can be attached to a more poroussubstrate, thereby yielding a composite self-assembled structure orcomposite membrane where the nanoporous layer of the block copolymerserves as the retentive layer and the more porous substrate layer servesas support. The support can be made of any suitable polymer, forexample, polyaromatics; sulfones (e.g., polysulfones, including aromaticpolysulfones such as, for example, polyethersulfone (PES), polyetherether sulfone, bisphenol A polysulfone, polyarylsulfone, andpolyphenylsulfone), polyamides, polyimides, polyvinylidene halides(including polyvinylidene fluoride (PVDF)), polyolefins, such aspolypropylene and polymethylpentene, polyesters, polystyrenes,polycarbonates, polyacrylonitriles ((PANS) includingpolyalkylacrylonitriles), cellulosic polymers (such as celluloseacetates and cellulose nitrates), fluoropolymers, and polyetheretherketone (PEEK).

Without wishing to be bound by any theory or mechanism, the formation ofa nanostructure is believed to take place as follows. The diblockcopolymer in solution experiences certain thermodynamic forces. Sincethe diblock copolymer comprises two chemically different blocks ofpolymer chains connected by a covalent bond, there exists anincompatibility between the two blocks. In addition, there exists aconnectivity constraint imparted by the connecting covalent bond. As aresult of these thermodynamic forces, the diblock copolymer whendissolved in an appropriate solvent system self-assemble into microphaseseparated domains that exhibit ordered morphologies at equilibrium. Whena film is cast from a dilute solution, the diblock copolymer formsmicelles composed of a core and a corona, each made of a differentblock. In dilute solution, the micelles tend to be isolated from eachother. However, in concentrated solution, as for example, when thesolvent is removed from a thin film of the solution by evaporation, themicelles tend to aggregate with the result that the coronas merge toform a continuous matrix and the cores merge to form porous channels.

The block copolymer's ability to form ordered structures depends on anumber of factors, including the polymer's relaxation rate, itsviscosity, its concentration, and the nature of the solvent, inparticular its chi parameter or the Hansen solubility parameter. Aneutral solvent to both the blocks tends to orient the cylindrical poresnormal to the membrane surface. The solvent system chosen to dissolvethe diblock copolymer provides the driving force for free energyminimization and formation of ordered structures. Accordingly, thechoice of the solvent or solvent system is an important factor inobtaining ordered nanostructures.

In accordance with an embodiment, the diblock copolymer self-assemblesinto a porous structure in a matrix assuming a hexagonal order in whichthe minor block forms the porous hexagonal domains in a matrix of themajor block. The minor block is the one composed of a monomer whosedegree of polymerization is less than that of the monomer constitutingthe major block. The pores in the hexagonal domain are about 60 nm toabout 80 nm in size, with an average size of about 70 nm. In anembodiment, the density of pores is 2.2×10¹⁵ pores/m².

In accordance with an embodiment of the invention, the porous membraneis a nanoporous membrane, for example, a membrane having pores ofdiameter between 1 nm and 100 nm.

A porous structure can be generated from the self-assembled structure,particularly one with cylindrical morphology, via a confined swellingstep, which is carried by annealing. The annealing step could be done ineither a solvent vapor or soaking in liquid solvent. The solvent shouldbe a good solvent for the minor volume fraction block that forms thecylinder core and non-solvent for the major volume block forming thematrix. While not intending to be held to any theory or mechanism, it isbelieved that, as the self-assembled structure is annealed the cylindercore becomes swollen by the solvent, leading to an increase of thecylinder volume. As the cylinder cores spread outside the matrixsurface, the spreading forces the cylinders to create pores. The matrixthickness also increases.

Examples of solvents that can be used for the annealing includetetrahydrofuran (THF), butylacetate, ethylacetate, methylethylketone,and acetone. The solvent or mixture of solvents can be at any suitabletemperature, for example, from ambient temperature, for example, 20° C.to 25° C., to elevated temperatures, such as up to 40° C., 50° C., 60°C., 70° C., 80° C., or 90° C.

Membranes according to embodiments of the invention can be used in avariety of applications, including, for example, diagnostic applications(including, for example, sample preparation and/or diagnostic lateralflow devices), ink jet applications, filtering fluids for thepharmaceutical industry, filtering fluids for medical applications(including for home and/or for patient use, e.g., intravenousapplications, also including, for example, filtering biological fluidssuch as blood (e.g., to remove leukocytes)), filtering fluids for theelectronics industry (e.g., filtering photoresist fluids in themicroelectronics industry), filtering fluids for the food and beverageindustry, clarification, filtering antibody- and/or protein-containingfluids, filtering nucleic acid-containing fluids, cell detection(including in situ), cell harvesting, and/or filtering cell culturefluids. Alternatively, or additionally, membranes according toembodiments of the invention can be used to filter air and/or gas and/orcan be used for venting applications (e.g., allowing air and/or gas, butnot liquid, to pass therethrough). Membranes according to embodiments ofthe inventions can be used in a variety of devices, including surgicaldevices and products, such as, for example, ophthalmic surgicalproducts.

In accordance with embodiments of the invention, the porous membrane canhave a variety of configurations, including planar, flat sheet, pleated,tubular, spiral, and hollow fiber.

Porous membranes according to embodiments of the invention are typicallydisposed in a housing comprising at least one inlet and at least oneoutlet and defining at least one fluid flow path between the inlet andthe outlet, wherein at least one inventive membrane or a filterincluding at least one inventive membrane is across the fluid flow path,to provide a filter device or filter module. In an embodiment, a filterdevice is provided comprising a housing comprising an inlet and a firstoutlet, and defining a first fluid flow path between the inlet and thefirst outlet; and at least one inventive membrane or a filter comprisingat least one inventive membrane, the inventive membrane or filtercomprising at least one inventive membrane being disposed in the housingacross the first fluid flow path.

Preferably, for crossflow applications, at least one inventive membraneor filter comprising at least one inventive membrane is disposed in ahousing comprising at least one inlet and at least two outlets anddefining at least a first fluid flow path between the inlet and thefirst outlet, and a second fluid flow path between the inlet and thesecond outlet, wherein the inventive membrane or filter comprising atleast one inventive membrane is across the first fluid flow path, toprovide a filter device or filter module. In an illustrative embodiment,the filter device comprises a crossflow filter module, the housingcomprising an inlet, a first outlet comprising a concentrate outlet, anda second outlet comprising a permeate outlet, and defining a first fluidflow path between the inlet and the first outlet, and a second fluidflow path between the inlet and the second outlet, wherein at least oneinventive membrane or filter comprising at least one inventive membraneis disposed across the first fluid flow path.

The filter device or module may be sterilizable. Any housing of suitableshape and providing an inlet and one or more outlets may be employed.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

Example 1

This example provides the materials used in the preparation of themonomers and polymers.

Maleimide, furan, diisopropylazodicarboxylate (DIAD), triphenylphosphine(Ph₃P), 1-haxadecanol, tetrahydrofuran (THF), ethyl acetate,N-phenylmaleimide, acetonitrile, methanol, Grubbs second generationcatalyst, 3-bromopyridine, and pentane were obtained from Sigma-AldrichCo. and used without further treatment. Dichloropentane, also obtainedfrom Sigma-Aldrich Co., was treated with basic alumina before use.

Example 2

This example illustrates the preparation ofexo-7-oxanorbornene-5,6-dicarboxyimide (C1), an intermediate in thepreparation of the first and second monomers in accordance with anembodiment of the invention.

In a clean 500 mL round bottom flask (RBF) equipped with magneticstirring bar, furan (21.0 g, 309 mmol) was added to a solution ofmaleimide (25 g, 258 mmol) in 250 mL of ethyl acetate. The mixture washeated at 90° C. for 30 h. C1 was obtained as white precipitate fromsolution upon washing with ether (100 mL, 3×) and filtration. The whitesolid was dried under vacuum at room temperature for 24 h. C1 wasobtained as a pure exo-isomer in yield of 29 g, 68%. ¹H-NMR (300 MHz,CDCl₃): δ (ppm) 8.09 (s, 1H), 6.53 (s, 2H), 5.32 (s, 2H), 2.89 (s, 2H).

Example 3

This example illustrates the preparation ofdichloro[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](benzylidene)bis(3-bromopyridine)ruthenium(II)(G3) catalyst.

The second generation Grubbs catalyst (G2) illustrated above (1.0 g,1.18 mmol) was mixed with 3-bromopyridine (1.14 mL, 11.8 mmol) in 50 mLflask. Upon stirring at room temperature for 5 min, the red mixtureturned into bright green. Pentane (40 mL) was added with stirring for 15minutes and green solid was obtained. The mixture was cooled in thefreezer for 24 h and filtered under vacuum. The resulting G3 catalyst, agreen solid, was washed with cold pentane and dried under vacuum at roomtemperature to give a yield of 0.9 g, 88% yield.

Example 4

This example illustrates the preparation of a first monomer inaccordance with an embodiment of the invention,exo-7-oxanorbornene-N-triethyleneglycolmonemethylether-5,6-dicarboxyimide).

A 1 L round-bottom flask was charged withexo-7-oxanorbornene-5,6-dicarboxyimide (82.6 g; 0.5 mol),triethyleneglycol monomethyl ether (70.4 mL; 0.45 mol) andtriphenylphosphine (144.3 g; 0.55 mol). The contents were vigorouslystirred with anhydrous tetrahydrofuran (650 mL) until all the solidsdissolved. The mixture was cooled in an ice-bath, followed by thedrop-wise addition of diethyl azodicarboxylate (87 mL; 0.55 mol) dilutedwith anhydrous tetrahydrofuran (50 mL), while maintaining vigorousstirring and ice cooling. The reaction mixture was allowed to slowlywarm up to ambient temperature and stirring continued for 24-48 h.Tetrahydrofuran was removed by rotary evaporation and the concentratewas diluted with diethyl ether (1 L) and the resulting slurry wasstirred at the ambient temperature for 4 h. The insoluble solids werefiltered off, washed with diethyl ether (2×150 mL) and the filtrate andwashes were combined and concentrated by rotary evaporation. Theresulting residue was diluted with distilled water (750 mL) withvigorous stirring. The precipitate was filtered off, washed with water(2×75 mL) and the filtrate and washes were combined and extracted withdiethyl ether (4×200 mL). The aqueous layer was then saturated by addingsolid NaCl followed by extraction with dichloromethane (5×200 mL). Theether and dichloromethane extracts were analyzed by TLC and thefractions deemed sufficiently pure were pooled, dried with anhydrousmagnesium sulfate, filtered and concentrated to constant weight. Theobtained yellow viscous liquid was judged by the NMR analysis to besufficiently pure for subsequent polymerizations. Product yield was 81.4g (60%). ¹H-NMR (300 MHz, CDCl₃): 6.51 (s, 2H), 5.26 (s, 2H), 3.65-3.72(m, 2H), 3.55-3.62 (m, 8H), 3.51-3.54 (m, 2H), 3.37 (s, 3H), 2.87 (s,2H).

Example 5

This example illustrates the preparation of a second monomerexo-7-oxanorbornene-N-phenyl-5,6-dicarboxyimide.

In a clean 500 mL round bottom flask (RBF) equipped with magneticstirring bar, Furan (29.51 g, 433.5 mmol) was added to a solution ofN-phenyl maleimide (25 g, 144.5 mmol) in 135 mL of acetonitrile. Thesolution was refluxed at 90° C. for 5 h. White crystalline solid wasobtained upon cooling the reaction mixture. The second monomer wasobtained by filtering the solid and purified by recrystallization fromacetonitrile (2×). Yield of 19 g, 76%. ¹H-NMR (300 MHz, CDCl₃): δ (ppm)7.55-7.35 (m, 3H, phenyl), 7.35-7.2 (m, 2H, phenyl), 6.57 (s, 2H), 5.37(s, 2H), 3.05 (s, 2H).

Example 6

The Grubbs 3^(rd) generation (G3) catalyst illustrated in Example 3(18.94 mg, 0.02 mmol) was weighed in a 40 mL vial equipped with afluoropolymer resin-silicone septa open-top cap. The G3 was dissolved inargon-degassed DCM (10 mL) and transferred via a cannula to a clean 1 LRBF equipped with stirring bar. A solution of the first monomer fromExample 4 (1.0 g, 3.21 mmol) in DCM (5 mL) was degassed with argon andtransferred into the G3 solution and shined for 70 minutes. An aliquotof 1-2 mL of the polymer block formed was taken after 65 minutes formolecular weight characterization. A solution of the second monomer(Example 5) (4.0 g, 16.6 mmol) in DCM (110 mL) was degassed with argonand transferred into the growing polymer block solution and was stirredfor another 60 minutes. Ethylvinylether (2 mL) was added to the yellowsolution of the diblock copolymer to terminate the reaction and allowedto stir for another 20 min. The resulting polymer was precipitated inMeOH (2 L, 2×) to recover the block copolymer as a white solid. Thepolymer was filtered and dried under vacuum at room temperature. ¹H-NMR(300 MHz, CDCl₃): δ (ppm) 7.7-7.25 (m, 3H, phenyl), 7.25-6.8 (m, 2H,phenyl), 6.3-5.9 (broad, 1H), 5.9-5.3 (broad m, 1H), 5.3-4.9 (broad m,1H), 4.9-4.2 (broad m, 1H), 4.0-2.90 (broad m, 19H).

Example 7

This example illustrates a method to characterize the diblock copolymerinvolving the Multi-angle Laser Light Scattering and gel permeationchromatography (GPC).

The homopolymer and diblock copolymer obtained in Example 6 wascharacterized for their molecular weight and molecular weightdistribution properties by the MALS-GPC technique under the followingconditions:

Mobile phase: Dichloromethane (DCM).

Mobile phase temperature: 30° C.

UV wavelength: 245 nm.

Columns used: three PSS SVD Lux analytical columns(Styrene-divinylbenzene copolymer network), columns have stationaryphase beads of 5 micrometers and has the pore sizes of 1000 A, 100,000A, and 1000,000 A, and guard columns.

Flow rate: 1 mL/min.

GPC system: waters HPLC alliance e2695 system with UV and RI detectors

MALS system: The DAWN HELEOS 8 system with 8 detectors operating a laserat 664.5 nm.

The chromatograms are depicted in FIG. 1. The diblock copolymer 2 elutedearlier than homopolymer 1 since it had a higher molecular weight.

Example 8

This example illustrates a method for preparing a self-assembledstructure in accordance with an embodiment.

The process involves preparation of a casting solution, casting a thinfilm followed by annealing the film in a good solvent for both blocks. A1.0% mass per volume solution of the diblock copolymer from Example 6was prepared in either a mixture of N,N-dimethylformamide (DMF) andtetrahydrofuran (THF) of 70/30 volume % composition or a mixture ofN,N-dimethylacetamide (DMAC) and 1-chloropentane 70/30 volume %composition or dichloromethane neat solvent. The solutions were stirredat room temperature for 3 days before they were used.

Thin films of each of the above polymer solutions were spin coated on aglass or silicon wafer substrate at spinning rates of 2000 rpm or 2500rpm. A Laurell WS-650MZ-23NPP Spin Processor was used to spin coat thepolymer solution. The films obtained were annealed in a DCM chamber foras few as 15 hours and for as long as 10 days. The films were thenimaged with atomic force microscopy (AFM) to reveal the orderednanostructure.

FIG. 2 depicts the AFM height image of the surface of a film spin coatedon glass surface at 2000 rpm. FIG. 3 depicts the AFM phase image of theself-assembled structure depicted in FIG. 2. Hexagonal order of theself-assembled structure is evident at least from the circled regions.

FIG. 4 depicts the profile showing the domain size and periodicity ofthe self-assembled structure in one of the circled regions of thestructure. FIG. 5 depicts the profile showing the domain size andperiodicity of the self-assembled structure in another circled region ofthe structure.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and “at least one” andsimilar referents in the context of describing the invention (especiallyin the context of the following claims) are to be construed to coverboth the singular and the plural, unless otherwise indicated herein orclearly contradicted by context. The use of the term “at least one”followed by a list of one or more items (for example, “at least one of Aand B”) is to be construed to mean one item selected from the listeditems (A or B) or any combination of two or more of the listed items (Aand B), unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

The invention claimed is:
 1. A method of preparing a self-assembledporous membrane comprising a diblock copolymer of the formula (I):

wherein: R¹ is a poly(alkyleneoxide) group of the formula,—(CHR—CH₂—O)_(p)-R′, wherein p=2-6, R is H or methyl, and R′ is H, aC₁-C₆ alkyl group, or a C₃-C₁₁ cycloalkyl group; R² is a C₆-C₂₀ arylgroup or a heteroaryl group, optionally substituted with a substituentselected from hydroxy, amino, halo, alkoxy, alkylcarbonyl,alkoxycarbonyl, amido, and nitro; one of R³ and R⁴ is a C₆-C₁₄ arylgroup, optionally substituted with a substituent selected from hydroxy,halo, amino, and nitro, and the other of R³ and R⁴ is a C₁-C₂₂ alkoxygroup, optionally substituted with a substituent selected from carboxy,amino, mercapto, alkynyl, alkenyl, halo, azido, and heterocyclyl; and nand m are independently about 10 to about 2000; wherein the volumefraction of the monomer bearing R² to that of the monomer bearing R¹ inthe block copolymer is about 3.5:1, and the membrane has a cylindricalmorphology; the method comprising: (i) dissolving the diblock copolymerin a solvent system to obtain a polymer solution; (ii) spin coating thepolymer solution onto a substrate; (iii) annealing the coating obtainedin (ii) to obtain a self-assembled porous membrane; and optionally (iv)washing the self-assembled porous membrane obtained in (iii).
 2. Themethod of claim 1, wherein R is H.
 3. The method of claim 1, wherein pis 3-6.
 4. The method of claim 1, wherein R′ is a C₁-C₆ alkyl group. 5.The method of claim 1, wherein R′ is methyl.
 6. The method of claim 1,wherein R² is a phenyl group, optionally substituted with a substituentselected from hydroxy, amino, halo, alkoxy, alkylcarbonyl,alkoxycarbonyl, amido, and nitro.
 7. The method of claim 1, wherein R³is phenyl.
 8. The method of claim 1, wherein R⁴ is a C₁-C₆ alkoxy group.9. The method of claim 1, wherein n is about 30 to about 350 and m isabout 150 to about
 1775. 10. The method of claim 1, wherein the diblockcopolymer of formula (I) has the following structure:


11. The method of claim 1, wherein the solvent system includes a solventor a mixture of solvents selected from halogenated hydrocarbons, ethers,amides, and sulfoxides.
 12. The method of claim 1, wherein the solventsystem includes a solvent or a mixture of solvents selected fromdichloromethane, 1-chloropentane, 1,1-dichloroethane, dimethylformamide,dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide,tetrahydrofuran, 1,3-dioxane, and 1,4-dioxane.
 13. The method of claim1, wherein the polymer solution contains about 0.1 to about 2% by weightof the diblock copolymer.
 14. The method of claim 1, wherein thesubstrate is selected from glass, silicon wafer, metal plate, plasticfilm, and a plastic film coated on a glass substrate or on a siliconwafer.
 15. The method of claim 1, wherein the substrate is porous. 16.The method of claim 1, wherein the annealing is carried out in thepresence of a solvent vapor.
 17. A self-assembled porous membraneprepared by the method of claim
 1. 18. The self-assembled porousmembrane of claim 17, wherein the diblock copolymer in the membrane hasa cylindrical morphology perpendicular to the plane of the membrane andthe membrane has pores whose diameters are in the range of about 40 to60 nm and pores extend all the way down to film thickness and at a depthof about 50 nm.
 19. The method of claim 1, wherein the solvent system isa mixture of dimethylformamide (DMF) and tetrahydrofuran (THF), amixture of dimethylacetamide (DMA) and THF, a mixture ofdimethylsulfoxide (DMSO) and THF, a mixture of DMSO and 1-chloropentane,a mixture of N-methylpyrrolidone (NMP) and 1-chloropentane, a mixture ofDMF and 1-chloropentane, a mixture of 1,3-dioxane and THF, a mixture of1,4-dioxane and THF, or a mixture of 1,3- or 1,4 dioxane, DMF, and THF.20. The method of claim 19, wherein the solvent system is a 70/30 volume% mixture of DMF and THF or a 70/30 volume % mixture of DMA and1-chloropentane.